<style>
    div {
                height: 100vh;
                background: rgba(0, 0, 0, .7);
                color: #fff;
                line-height: 100vh;
                text-align: center;
                font-size: 20vh;
            }
    
            .a-img1 {
                background-image: url(https://images.pexels.com/photos/1097491/pexels-photo-1097491.jpeg);
                background-attachment: fixed;
                background-size: cover;
                background-position: center center;
            }
    
            .a-img2 {
                background-image: url(https://images.pexels.com/photos/2437299/pexels-photo-2437299.jpeg);
                background-attachment: fixed;
                background-size: cover;
                background-position: center center;
            }
    
            .a-img3 {
                background-image: url(https://images.pexels.com/photos/1005417/pexels-photo-1005417.jpeg);
                background-attachment: fixed;
                background-size: cover;
                background-position: center center;
            }
    </style>
     <div class="a-text">1</div>
        <div class="a-img1">2</div>
        <div class="a-text">3</div>
        <div class="a-img2">4</div>
        <div class="a-text">5</div>
        <div class="a-img3">6</div>
        <div class="a-text">7</div>